Aerosol spray can with pressure reducing valve

ABSTRACT

For a pressure reduction, an aerosol spray can filled with a compressed pressure gas requires, upstream of its spray valve (14), a pressure regulation valve (10) with a closing point (28). In known embodiment types a flow occurs around the outside of the pressure reduction valve, which requires a complicated housing structure. It is therefore proposed that the connection between the closing point (28) and the spray valve (14) take place via a central bore (58) in the piston (22) of the pressure reduction valve (10), preferably without a flow through the pressure chamber (26), but instead past the latter. The simple construction is advantageous, with which it is also possible to provide easy access to the piston (22) from the outside in order to maintain it in its opened position for easier filling under pressure.

The invention relates to an aerosol can with a pressure reduction valvebetween the interior of the can and a spray valve, wherein, viewed inthe outflow direction downstream of a closing site, a pressure chamberis provided for pressure regulation, in which a piston can be movedwhich closes the closing point against the force of a spring, forexample a helical spring or a gas pressure spring, when pressure in thepressure chamber rises above the standard pressure.

For regulating the pressure in connection with aerosol cans filled withcompressed gases, it is required to install a pressure regulating valveupstream of the spray valves which, with a filling pressure ofapproximately 10 bar inside the can, provides a standard pressure ofapproximately 2 to 4 bar. Pressure reduction valves with spring-loadedpistons are already known for this purpose, which provide the closing ofa pressure-regulated closing site when the regulated pressure rises.However, with the known solutions the exiting aerosol flows around thecylinder/piston unit, so that an elaborate dual-walled housing structureis required. Such a solution has been described, for example, in WO01/09009 A1.

The object of the present invention is to create a spray can with apressure reduction valve which is easier to produce in comparison withalready known embodiments.

In accordance with the invention, this object is attained by means of aspray can of the type described at the outset, wherein the connectionbetween the closing site for pressure regulation and the spray valve isprovided by means of a center bore in the piston.

The aerosol spray can in accordance with the invention offers theadvantage that it is not necessary to provide an additional housing wallfor conducting the aerosol around the cylinder/piston unit, so that theproduction outlay is reduced. The slightly increased thickness, forexample of a piston rod used for regulating the closing site, poses noproblems here.

In a preferred embodiment of the aerosol spray can in accordance withthe invention there is no flow-through of the pressure chamber, so thatan effect by dynamic occurrences on the accuracy of regulation in thearea of the piston must only be feared to a lesser degree.

In a particularly preferred embodiment of the invention it is providedthat the piston of the pressure reduction valve is accessible from theoutside in such a way that it can be mechanically moved into itsposition in which it clears the closing site.

Such an embodiment, which can only be achieved with a large outlay inconnection with a pressure reduction valve around which an outer flowoccurs, permits a problem-free filling process, in which the piston isprevented from moving into its closed position, or at least into aposition in which its opening cross section is reduced and the fillingprocess therefore made more difficult under the very high pressurecharge from the outside then occurring. An end stop preferably limitsthe opening stroke in order to prevent in this case damage to undefinedcontact points between the piston and the housing.

Alternatively to a mechanical displacement of the piston in its positionin which it releases the closing site, the provision of some sort ofoverpressure valve is also conceivable which, in case of a pressurecharge from the outside which considerably exceeds the interior canpressure, clears an opening to the can interior. However, this means anincreased structural outlay.

In a preferred embodiment of the invention,it is provided that theclosing site is formed between a sealing element fixed on the housingand a piston rod, or a separate element, which can be axially movedthrough the piston.

In the simplest case the piston and the piston rod can be embodied inone piece, wherein the sealing element preferably rests against theexterior circumference of the piston rod and closes a radial opening toits central bore in the closing site. With such a solution it is alsoconceivable that the sealing element clears the closing site in case ofa pressure charge from outside which considerably exceeds the interiorcan pressure.

It is also alternatively conceivable to provide a separate closingelement for forming the closing site with the sealing element, which canbe moved into a position where it is lifted off the sealing element bymeans of a piston rod in case of a pressure drop.

The connection between the pressure chamber and the areas through whichthe flow passes can be provided either by means of an annular groovearound the piston rod, which is connected with the closing site, or alsoby means of a radial bore in the piston rod, which provides the requiredactive connection without the exiting aerosol flowing through thepressure chamber.

Embodiments of piston rods without radial bores are open at their frontends and are embodied to be laterally slit in this area in order toassure the flow-through of the aerosol.

A particular advantage of the aerosol spray can of the invention lies inthat it is possible to provide a housing for the pressure reductionvalve which supports the sealing element of the closing site and whoseexterior wall delimits the pressure chamber on the inside. The spring ofthe pressure reduction valve, which is embodied as a helical spring or agas pressure spring, is arranged between the housing and the piston,wherein the spring is preferably supported on a housing insert, which islocked, pressed, welded and/or glued together with the cylinder wall ofthe housing. The space between the housing and the piston in which thespring is arranged is preferably pressure-sealed toward the can interiorin order to avoid an effect on the pressure regulation by penetratingaerosol. The space-saving construction of the pressure valve of a spraycan in accordance with the invention permits the provision of thelargest possible piston diameter, along with a corresponding adaptationof the force of the piston spring, and in this way the optimization ofthe regulation accuracy. A pressure gas cushion, which constitutes a gaspressure spring, can also be enclosed in the sealed space between thehousing and the piston.

Exemplary embodiments will be discussed in greater detail by means ofthe attached drawings in what follows. Shown are in:

FIG. 1, a cross section of a pressure reduction valve of a spray can inthe pressureless, empty state of the can,

FIG. 2, the pressure reduction valve in FIG. 1 in the closed position ofrest after the can has been filled,

FIG. 3, a cross section of a further embodiment of a pressure reductionvalve in the pressureless, empty state of the can,

FIG. 4, the pressure reduction valve in FIG. 3 in its position of restafter the can has been filled.

A pressure reduction valve 10 is represented in FIG. 1, which issealingly connected with a valve cover 12, preferably made of a thinsheet of metal or of aluminum, which in turn closes an aerosol spray can(not represented) in a pressure-sealed manner. A spray valve, not shownin greater detail, by means of which the directed spraying of thecontents of the can is made possible by pushing down a spray head, isprovided in the head area of the pressure reduction valve 10.

The pressure reduction valve 10 substantially consists of a housing 16which, in its rear, cylindrically embodied area 18 is closed by means ofa housing insert 20, which provides the connection with the valve cover12 and receives the spray valve 14, a movable piston 22, which is inequlibrium between a compression spring 24 and a regulating pressure ina pressure chamber 26 acting on its piston face, and a closing site 28for pressure regulation, which can be actuated by means of the piston 22via a piston rod 30. The housing 16 constitutes the outer wall of thepressure chamber 26 and supports a sealing element 32, embodied as anO-ring, and which, together with a closing element 34 which is movablein the housing 16 coaxially in respect to the piston 22, constitutes theclosing site 28. With the piston 22 displaced by pressure against theforce of its spring 24, a securing spring 36 maintains the closingelement 34 sealingly on the sealing element 32.

The connection between the pressure chamber 26 and the closing site 28takes place via an annular conduit 38, which surrounds the piston rod 30and which is bordered from the outside by a holding insert 40, whichconstitutes an axial support for the sealing element 32.

In FIGS. 1 to 4, the pressure spring is represented alternatively in theform of a helical spring 24 (right halves of the drawing figures) and inthe form of an enclosed pressure gas cushion 27 (left drawing figurehalves).

Sealing of the space 25 for receiving the helical spring 24 between thehousing 16 and the piston 22 is provided by means of an O-ring 42between the piston 22 and the inner wall of the housing 16, and twoadditional O-rings between a holding element 44, inserted into thehousing and also used for supporting the helical spring 24, and theinner wall of the housing 16, or the outer wall of the piston rod 30 inthis area. A stop 46 limits the stroke of the piston 22 in the area ofthe housing insert 20, while a second stop 48 provided on the side ofthe housing limits the stroke of the piston 22 in the opened position.

The outflow of the aerosol initially takes place through a tube or hose50 extending into the vicinity of the bottom of the aerosol spray can, ahousing connector 52 terminating in the chamber of the housing 16 whichcontains the closing element 34, then on through slits 54 in the frontface of the stop 48, which provide a flow cross section even when theyrest against the second stop, through longitudinal grooves 53 in thehousing 16, along the outside of the closing element 34 through secondslits 56 in the front area of the piston rod 30 into a central bore 58in the piston rod and up to the spray valve 14, known per se, with itsspray head (not shown in detail). The regulating pressure which must beset between the closing site 28 and the spray valve 14 also acts via theannular groove 38 in the pressure chamber 26, without aerosol flowingthrough the latter. An exchange of the aerosol in the pressure chamber26 takes place through inflow and outflow in the course of the strokemovements of the piston 22. A continuous flow through the pressurechamber is also conceivable if the inlet opening of the central bore 58is arranged in the area of the pressure chamber 26.

In the initial position of the pressure regulating valve represented inFIG. 1, the can has not yet been filled, i.e. the can interior is notunder pressure, and the compression spring 24 can displace the piston 22and the closing element 34 against the second stop 48, so that theconnection between the spray valve 14 and the can interior is open. Thesecuring spring 36 is compressed by the force of the stronger spring 24of the piston 22.

For filling the can it is possible to maintain the piston 22mechanically in this opened position by means of a depressor 60, whichhere is constituted by the so-called stem, in order to be able to chargethe can with a high filling pressure for accelerating the fillingprocess, without a reduction in the cross section at the closing site 28occurring because of the pressure increasing in the pressure reductionvalve 10. At the end of the filling process, the depressor 60 isreleased, so that the piston can be displaced into its positionrepresented in FIG. 2 under the high interior pressure in the aerosolspray can. In this position the piston rod 30 is lifted off the frontface of the closing element 34, and the latter is pressed against thesealing element 32 by the force of the securing spring 36 and with theaid of the interior can pressure as soon as the desired regulatingpressure of approximately 3 bar has been reached in the pressure chamber26.

If, following an opening of the spray valve 14, the pressure in the areabetween the spray valve 14 and the closing point 28 drops, the forceexerted by the pressure on the piston 22 falls, so that the compressionspring 24 again starts to displace the piston while taking along theclosing element 34 until, following the lift-off of the closing element34 from the sealing element 32 and the possible inflow of aerosol, theregulating pressure has again been reached in the pressure chamber 26and leads to the closing of the closing site 28. An equilibrium isreached in the area of the closing site 28 during continuous spraying ofthe contents of the can and provides the desired pressure drop, withouta continuously repeated closing movement of the piston 22 occurring.

For improving the regulating accuracy it is desirable to provide thelargest possible piston diameter, wherein the force of the compressionspring 24 must of course be matched to the desired regulating pressure.

A further embodiment of a pressure reduction valve 110 is represented incross section in FIG. 3, which in its essential parts corresponds to theembodiment represented in FIGS. 1 and 2. Therefore identical parts havebeen provided with identical reference numerals.

Differences exist in the area of a differently embodied closing site 128and a piston rod 130, modified in its lower area 156 which, togetherwith a washer 132 clamped between a holder insert 140 and a housingshoulder 141, constitutes the closing site 128. The piston rod 130,which is again provided with a bore 58, is closed on its front end 131,wherein slits 154 are again provided in the area of the housing stop 48,which allow the inflow of aerosol out of the housing connector 52 intoan annular chamber 129 provided in the area of the closing point.

The piston rod has a first radial bore 137 which, in the opened positionof the piston 22, provides a connection between the annular chamber 129and the bore 58 in the piston 22. A second radial bore provides aconnection between the bore 58 in the piston 22 and the pressure chamber26 in order to be able to perform the desired pressure regulation asalready explained in connection with FIGS. 1 and 2.

In the position represented in FIG. 3, which the pressure reductionvalve 110 assumes with the spray can unfilled and not under pressure,the piston rod 130 of the piston is seated on the second housing stop 48by means of the force of a compression spring 24. In this case the firstradial bore 137 is located axially offset in respect to the washer 132,so that its cross section is open.

After filling the spray can under pressure, which again takes place, ifrequired, with the help of the depressor 60 which holds the piston 22fast in a position which increases the opening cross section of theclosing site 128, the piston takes up the position represented in FIG.4, in which the pressure prevailing in the pressure chamber 26 displacesthe piston against the force of the pressure spring 24, so that theradial bore 137 is moved into an area downstream of the washer 132,which sealingly rests against the outer circumference of the piston rod130 and in this way seals the high interior can pressure ofapproximately 10 bar, which prevails in the housing connector 52,against the areas downstream of the washer 132 as far as the spray valve14 at a regulating pressure of approximately 3 bar. A moving hook 134,which can also be embodied to be in the shape of a ring over the entirecircumference, here provides the optimum positioning of the washer inorder to assure a good sealing effect over a long time.

Further embodiments of details are of course conceivable, for example,in the embodiment represented in FIGS. 1 and 2, the radial bore 138 canreplace the annular conduit 38, or it can be provided in a complementarymanner and, as already mentioned, it is also possible to employ gaspressure springs with appropriate characteristic lines besides thehelical springs. In general, it is possible to improve the accuracy ofregulation by increasing the ratio of the diameters between the sealingpoint constituted by the O-ring 42 and that of the sealing element 32,or the washer 132 in the area of the closing sites 28, 128. Since thediameter of the sealing element 32, or of the washer 132 cannot bearbitrarily reduced, an increased piston diameter can be sensible,however, the can volume should not be reduced too greatly. For mostapplications it has been shown to be sufficient for attempting aregulating pressure between 2 and three bar, wherein fluctuations withinthis range are quite safe and can be easily achieved with geometricconditions which meet the practical needs.

The pressure reduction valve 10 does not necessarily have to be astructural unit together with the spray valve. Instead, it isconceivable to produce the pressure reduction valve separately and thento connect it upstream of the spray valve by means of a hose or tube.Although in that case the embodiment of a depressor is possible only ina limited way, there is the possibility of falling back on existingproduction facilities for valve heads with spray valves.

What is claimed is:
 1. An aerosol spray can comprising: a pressurereduction valve provided between a can interior and a closeable sprayvalve, wherein, viewed in an outflow direction downstream of a closingsite, a pressure chamber is provided for pressure regulation, in whichpressure chamber a piston can be moved which closes the closing siteagainst a force of a spring, when pressure in the pressure chamber risesabove a standard pressure, and wherein a connection between the closingsite and the spray valve takes place via a central bore in the piston.2. The aerosol spray can in accordance with claim 1, characterized inthat the pressure chamber is arranged outside of a flow-through.
 3. Theaerosol spray can in accordance with claim 1, characterized in that:with the pressure reduction valve mounted in the aerosol can, the pistonis accessible from outside such that the piston can be mechanicallymoved into a position in which the piston releases the closing site, anda final stop for limiting an opening stroke is provided.
 4. The aerosolspray can in accordance with claim 1, characterized in that: the closingsite is formed between a sealing element fixed on a housing and aseparate closing element which can be axially moved through the piston,and wherein the sealing element preferably rests against the separateclosing element which separate closing element is provided forconstituting the closing site, and which separate closing element can bemoved by means of a piston rod into a position in which the separateclosing element is lifted off the sealing element when a pressure dropoccurs.
 5. The aerosol spray can in accordance with claim 4,characterized in that in a front area the piston rod is open and haslateral slits.
 6. The aerosol spray can in accordance with claim 4:characterized in that the outer wall of the housing supporting thesealing element delimits the pressure chamber on the inside, and whereinthe spring is arranged between the housing and the piston, and wherein aspace between the housing and the piston in which the spring is arrangedis pressure-sealed against the can interior.
 7. The aerosol spray can inaccordance with claim 6, characterized in that an insert is locked,pressed, welded and/or glued together with the cylinder wall of thehousing for supporting the spring on the housing.
 8. The aerosol spraycan in accordance with claim 1, wherein the spring is a helical spring.9. The aerosol spray can in accordance with claim 1, wherein the springis a pressure spring.
 10. The aerosol spray can in accordance with claim1, characterized in that: the closing site is formed between a sealingelement fixed on a housing and a piston rod which can be axially movedthrough the piston, wherein the sealing element preferably rests againstthe outer circumference of the piston rod and in the sealing positionseals a radial opening in the central bore towards the can interior. 11.The aerosol spray can in accordance with claim 10, characterized inthat: the pressure chamber extends around some areas of the piston rodand a radial bore is provided for connecting the pressure chamber withthe bore in the piston rod.
 12. The aerosol spray can in accordance withclaim 10, characterized in that a predetermined opening point isprovided which, in case of a pressure charge from the outside of apressure which considerably exceeds the interior can pressure, releasesan opening toward the can interior, wherein the sealing elementpreferably releases the closing site in case of a pressure charge fromthe outside which considerably exceeds the interior can pressure. 13.The aerosol spray can in accordance with claim 12: characterized in thatthe outer wall of the housing supporting the sealing element delimitsthe pressure chamber on the inside, wherein the spring is arrangedbetween the housing and the piston, and wherein a space between thehousing and the piston in which the spring is arranged ispressure-sealed against the can interior.
 14. A pressure reduction valvefor employment with an aerosol spray can comprising: wherein, viewed inan outflow direction downstream of a closing site, a pressure chamber isprovided for pressure regulation, in which pressure chamber a piston canbe moved which, when pressure in the pressure chamber rises above astandard pressure, closes a closing site against a force of a spring,characterized in that the * can be connected upstream by means of ahose, tube, or the like, and that the connection between the closingsite and the spray valve takes place via a central bore in the piston.